A 29-year-old man who says he is a former undercover CIA employee said Sunday that he was the principal source of recent disclosures about ­top-secret National Security Agency programs, exposing himself to possible prosecution in an acknowledgment that had little if any precedent in the long history of U.S. intelligence leaks.

Edward Snowden, a tech specialist who has contracted for the NSA and works for the consulting firm Booz Allen Hamilton, unmasked himself as a source after a string of stories in The Washington Post and the Guardian that detailed previously unknown U.S. surveillance programs. He said he disclosed secret documents in response to what he described as the systematic surveillance of innocent citizens.

In an interview Sunday, Snowden said he is willing to face the consequences of exposure.

“I’m not going to hide,” Snowden told The Post from Hong Kong, where he has been staying. “Allowing the U.S. government to intimidate its people with threats of retaliation for revealing wrongdoing is contrary to the public interest.”

Asked whether he believes that his disclosures will change anything, he said: “I think they already have. Everyone everywhere now understands how bad things have gotten — and they’re talking about it. They have the power to decide for themselves whether they are willing to sacrifice their privacy to the surveillance state.”

Snowden said nobody had been aware of his actions, including those closest to him. He said there was no single event that spurred his decision to leak the information, but he said President Obama has failed to live up to his pledges of transparency.

“My sole motive is to inform the public as to that which is done in their name and that which is done against them,” he said in a note that accompanied the first document he leaked to The Post.

The Guardian was the first to publicly identify Snowden, at his request.

The White House said late Sunday that it would not have any comment on the matter.

In a brief statement, a spokesman for the Office of the Director of National Intelligence said the intelligence community is “reviewing the damage” the leaks have done. “Any person who has a security clearance knows that he or she has an obligation to protect classified information and abide by the law,” said the spokesman, Shawn Turner.

Snowden said he is seeking “asylum from any countries that believe in free speech and oppose the victimization of global privacy,” but the law appears to provide for his extradition from Hong Kong, a semiautonomous territory of China, to the United States.

Although any extradition proceeding could take months or even years, experts said Snowden has not put himself in a favorable position.

“The fact that he outed himself and basically said, from what I understand he has said, ‘I feel very comfortable with what I have done’ . . . that’s not going to help him in his extradition contest,” said Douglas McNabb, a lawyer and extradition expert.

The Justice Department said it is in the “initial stages of an investigation” into the unauthorized disclosure of classified information but declined to comment further.

A stunning revelation

Current and former U.S. intelligence officials said the revelation of Snowden’s role in the leaks will lead to a sweeping reexamination of security measures at the CIA and the NSA, and they described his decision to come forward as a stunning conclusion to a week of disclosures that rattled the intelligence community.

“This is significant on a number of fronts: the scope, the range. It’s major, it’s major,” said John Rizzo, a former general counsel of the CIA who worked at the agency for decades. “And then to have him out himself . . . I can’t think of any previous leak case involving a CIA officer where the officer raised his hand and said, ‘I’m the guy.’ ”

A half-dozen former intelligence officials, including one who now works at Booz Allen Hamilton, said they did not know Snowden or anything about his background. Several former officials said he easily could have been part of a surge in computer experts and technical hires brought in by the CIA in the years after the Sept. 11, 2001, attacks as its budget and mission swelled.

“Like a lot of things after 9/11, they just went on a hiring binge, and in the technical arena young, smart nerds were in high demand,” a former U.S. intelligence official said. “There were battalions of them.”

Officials said the CIA and other spy agencies did not relax their screening measures as the workforce expanded. Still, several officials said the CIA will now undoubtedly begin reviewing the process by which Snowden may have been hired, seeking to determine whether there were any missed signs that he might one day betray national secrets.

More broadly, the CIA and the NSA may be forced to reexamine their relationships with contractors, who were employed in roles ranging from technical support to paramilitary operations before concerns about the outsourcing of such sensitive assignments prompted a backlash in Congress and pledges from the agencies to begin thinning their contracting ranks.

Some former CIA officials said they were troubled by aspects of Snowden’s background, at least as he described it to The Post and the Guardian.

For instance, Snowden said he did not have a high school diploma. One former CIA official said that it was extremely unusual for the agency to have hired someone with such thin academic credentials, particularly for a technical job, and that the terms Snowden used to describe his agency positions did not match internal job descriptions.

Snowden’s claim to have been placed under diplomatic cover for a position in Switzerland after an apparently brief stint at the CIA as a systems administrator also raised suspicion. “I just have never heard of anyone being hired with so little academic credentials,” the former CIA official said. The agency does employ technical specialists in overseas stations, the former official said, “but their breadth of experience is huge, and they tend not to start out as systems administrators.”

A former senior U.S. intelligence official cited other puzzling aspects of Snowden’s account, questioning why a contractor for Booz Allen at an NSA facility in Hawaii would have access to something as sensitive as a court order from the Foreign Intelligence Surveillance Court.

“I don’t know why he would have had access to those . . . orders out in Hawaii,” the former official said.

The Guardian initially reported the existence of a program that collects data on all phone calls made on the Verizon network. Later in the week, the Guardian and The Post reported the existence of a separate program, code-named PRISM, that collects the Internet data of foreigners from major Internet companies.

Snowden expressed hope that the NSA surveillance programs will now be open to legal challenge for the first time. This year, in Amnesty International v. Clapper, the Supreme Court dismissed a lawsuit against the mass collection of phone records because the plaintiffs could not prove exactly what the program did or that they were personally subject to surveillance.

“The government can’t reasonably assert the state-secrets privilege for a program it has acknowledged,” Snowden said.

Journalists criticized

Snowden’s name surfaced as top intelligence officials in the Obama administration and Congress pushed back against the journalists responsible for revealing the existence of sensitive surveillance programs and called for an investigation into the leaks.

Clapper, in an interview with NBC that aired Saturday night, condemned the leaker’s actions but also sought to spotlight the journalists who first reported the programs, calling their disclosures irresponsible and full of “hyperbole.” Earlier Saturday, he issued a statement accusing the media of a “rush to publish.”

“For me, it is literally — not figuratively — literally gut-wrenching to see this happen because of the huge, grave damage it does to our intelligence capabilities,” Clapper said.

On Sunday morning, before Snowden’s unmasking, House Intelligence Committee Chairman Mike Rogers (R-Mich.) had harsh words for the leaker and for the journalist who first reported the NSA’s collection of phone records, the Guardian’s Glenn Greenwald.

Greenwald “doesn’t have a clue how this thing works; neither did the person who released just enough information to literally be dangerous,” Rogers said on ABC’s “This Week,” adding: “I absolutely think [the leaker] should be prosecuted.”

Senate Intelligence Committee Chairman Dianne Feinstein (D-Calif.) agreed that whoever leaked the information should be prosecuted, and she sought to beat back media reports suggesting that the Obama administration overplayed the impact of the programs.

After opponents of the programs questioned their value last week, anonymous administration officials pointed to the thwarting of a bomb plot targeting the New York City subway system in 2009. Soon after, though, reporters noted that public documents suggested that regular police work was responsible for thwarting the attack, rather than a secret government intelligence program.

Feinstein said the programs were valuable in both the New York case and in another involving an American plotting to bomb a hotel in India in 2008. She noted that she could talk about those two cases because they have been declassified, but she suggested that the surveillance programs also assisted in other terrorism-related cases.

A chief critic of the efforts, Sen. Rand Paul (R-Ky.), said he is considering filing a lawsuit against the government and called on 10 million Americans to join in.

“I’m going to be asking all the Internet providers and all of the phone companies, ask your customers to join me in a class-action lawsuit,” Paul said on “Fox News Sunday.”